Does the ground glass eventually need cleaning?

[Philippe Gauthier]

I am amazed by the difference of luminosity between the ground glasses of my two view cameras. Both have normal GG, not fresnel or anything special, and the most luminous of the two has a lens that only opens to f/8, while the darker one opens to f/4.5. So, what's the difference? The difference of grinding can only account for so much difference, so I suppose that the GG of the murkier one must be dirty, covered with athmospheric goo, cigarette smoke and whatever else, accumulated over 75 years or so.

Is this a reasonable assumptions? And if yes, how would you clean a GG to restore it to its original luminosity (cleaning products, type of cloth, etc). A GG isn't that precious but it sounds silly to buy one.

[Brian Kennedy]

My camera is still relatively new, so my GG hasn't really needed much cleaning. But I have cleaned off some marks left by the rubberized end of my loupe a few times. I just used lens cleaner and a microfiber cloth and didn't really think about it.

I hate to state the obvious, because I am sure you realize this already. However, are you comparing similar focal lengths? As you probably know, wide angles are notoriously more difficult to see on the GG, since the edges hit the GG at more of an angle. For example, my 90/8 is noticeably more dim on the GG than my 300/9, especially around the edges.

[Ralph Barker]

In some areas, a drinking glass left out in the air for a couple of days will show signs of atmospheric contamination. So, I'd guess a ground glass would do the same after a while. For a regular ground glass without a fresnel that can be easily removed from the camera, I'd think that a blast of canned air, followed by warm water and a mild detergent or shampoo (e.g. baby shampoo) would do the trick. I'd use something like a 1/2" camelhair artist's brush to swish the soap around. Something that won't leave a residue within the ground surface, and that would allow air drying (aided, perhaps, by a hair drier). For the smooth rear surface, I just use lens cleaner and a clean cotton cloth.

[mark blackman]

my GG was getting a bit grubby so I put it in the dishwasher, came up a treat.

[Bill Jefferson]

I use windex and a soft cloth

[David A. Goldfarb]

Careful if your groundglass has grid lines or format markings. Some of them can be washed off easily, so be sure to test any cleaner you use in a non-critical area first.

[Philippe Gauthier]

No, no grids or whatever. It's a very basic camera, a king of Korona clone from the 1920's (lots of cool movements, though). The glass has probably never been cleaned, or then a loooong time ago. My other camera is much older (!) but has been very recently restored and cleaned. What a difference!

Thanks for the advice... and for not laughing at me. Such a basic question!

[Philippe Gauthier]

Err... Typo: "a kind of Korona", not a king. I'm not a monarchist. ;-)

[Larry Gebhardt]

With no grid lines you can just use glass cleaner and a paper towel. Glass is pretty durable.

[Philippe Gauthier]

Yep. I just did it. Windex + paper towel. The frosty side was surprisingly dirty. The GG looks a bit more luminous now, but of course only tests in real life situations will really tell.

[Conrad Hoffman]

No big deal to clean, but the grind does make a large difference in what you see, visibility of corners, and brightness. All ground glasses are a compromise- too fine and you can't see the edges, but the center will be quite bright. Too coarse and the illumination will be dim but even. The method of grinding probably has an effect as well. I prefer a true grind using another piece of glass and different grades of abrasive, compared to sandblasting and etching methods.